The decision to use a vacuum extractor instead of forceps in assisted vaginal delivery is based on the clinical situation and the experience and expertise of the doctor. For many physicians, these two instruments are interchangeable, while others feel more comfortable with one or the other. The use of the vacuum extractor has recently increased while the number of forceps deliveries has declined. Therefore, it is possible that a physician may have more experience using the vacuum extractor and this may be a key factor in the final decision. The advantages and disadvantages of these two methods are discussed below.
- Less injury to the mother's soft tissues. The vacuum extractor has consistently been associated with less injury to the mother's soft tissues than forceps. Trauma to the vaginal walls and to the vaginal opening is decreased due to easy placement of the instrument on the top of the baby's head. The vacuum extractor does not increase the width of the presenting part of the fetus as can happen with forceps. The amount of vaginal trauma is directly related to how much control the physician has over the force of the traction. In most cases, the amount of traction that can be applied by the vacuum is less than that produced by the forceps; therefore, the descent of the baby's head occurs in a more controlled fashion when the vacuum is used. When the head is delivered slowly, less tearing occurs.
- Ease of placement. A big advantage of the vacuum extractor is that it is easier to place than the forceps. Because of its design, the vacuum may be applied to the top of the baby's head as it becomes visible in the birth canal. The newer, soft plastic cups are pliable and can be folded for insertion and maneuverability. Forceps, on the other hand, must encircle the baby's head and therefore it is extremely important to know the exact position of the baby's head. There is also significant risk of injury to the vaginal walls during placement of the forceps. If the baby's head is tilted slightly to one side (asynclitic presentation), application of the forceps may be impossible. There are, however, contraindications to vacuum placement when the baby's head is in certain positions, so it is a requirement, nonetheless, to know the position of the baby's head.
- Less anesthesia is required. Because the vacuum extractor is easier to apply and is associated with less trauma to the vagina, it requires less anesthesia. Although epidural anesthesia is preferable, vacuum extraction may be performed after injection of local anesthetic that numbs the lower vagina. When regional anesthesia (epidural or spinal block) is not possible because of time constraints or unavailability, vacuum extraction may be performed safely and comfortably after local injection of medication.
- Fewer bowel problems. Some investigators have suggested that vacuum-assisted vaginal delivery results in less bowel incontinence compared to forceps delivery; most likely, this is due to potential for more vaginal trauma with forceps. The forceps-assisted vaginal delivery is more likely to result in vaginal tears that partially involve or even completely transect the anal sphincter and rectal lining. This type of injury is referred to as a fourth-degree laceration and can be associated with long-term anal sphincter dysfunction, resulting in occasional leakage of stool or gas.
- Less force is applied to the baby's head. Vacuum extraction exposes the baby to less traction in comparison to forceps delivery. One study found that vacuum extraction exerted approximately 40% less force to the baby's head than forceps delivery. Although vacuum delivery may be associated with development of a bruise on top of the baby's head, the forceps may cause similar injuries and may result in more serious nerve or skull injuries.
- The vacuum cup may become dislodged. When the second stage of labor has been prolonged, it is common to find that the baby's head has a significant amount of swelling at the presenting point. Although this is a normal part of labor, if the swelling is significant, it may be difficult to obtain an optimal application of the cup against the baby's head and the cup may become detached. Improper placement of the vacuum cup may also result in detachment.
- Vacuum extraction should be used only in full-term infants. Because of an increased risk of bleeding in the brain in premature infants, the vacuum extractor should be used only in term infants. This limits the use of vacuum extraction to deliveries at 34 weeks of gestation or later. Forceps may be used safely to deliver preterm babies.
- Delivery may take longer. Vacuum traction should be applied only during contractions; therefore, vacuum-assisted vaginal delivery may be slower than forceps delivery. Forceps delivery may be performed with very little maternal effort, while vacuum-assisted delivery requires maternal participation.
- Success rates are slightly lower for vacuum deliveries. Several large trials comparing the success of forceps delivery with that of vacuum-assisted delivery confirmed that forceps are more often successful in delivering the baby.
- Intracranial hemorrhage is more common. It has been well documented that the risk of serious bleeding inside the baby's skull is greater with vacuum than forceps. Due to the pressure of the suction cup applied to the baby's head, a particular type of serious bleeding, though rare, is more common with and unique to vacuum delivery
It is currently estimated that 10 to 15% of all babies born in the are delivered via operative vaginal delivery, of which about two-thirds are forceps deliveries and the remainder are vacuum deliveries. The great majority of these forceps deliveries are outlet or low-forceps deliveries. These deliveries pose little or no risk to mother or baby and are an advantage in some situations. For example, a baby who is shown to have an abnormal heart rate (either by use of a fetal heart rate monitor or monitoring with a stethoscope) can be safely delivered by outlet or low forceps delivery and promptly evaluated with resuscitation as needed. Likewise, a woman who has been in the second stage of labor for several hours, who is unable to make further progress for whatever reason, and whose baby is at a station and position consistent with an outlet or low forceps delivery, will clearly benefit from such an operative vaginal delivery, with negligible risks to her baby. Finally, a woman who has a medical condition that prevents her from pushing in the second stage of labor can benefit from an assisted vaginal delivery. The most common examples of this include women with significant heart disease, respiratory compromise, or certain neurologic conditions.
Forceps delivery places a woman at higher risk for blood transfusion and infection than does spontaneous vaginal delivery. However, compared to women who deliver by cesarean section following the onset of labor, women who deliver with forceps have significantly lower rates of these complications.
An additional benefit of forceps delivery is the avoidance of a surgical scar in the uterus (compared to cesarean section). This is particularly significant if she plans to have additional pregnancies. Women with histories of cesarean section have increased risks in subsequent pregnancies (whether they opt to attempt labor first or plan for repeat cesarean) that may have been prevented by successful vaginal birth (with the use of forceps or not) in the previous pregnancy.
Potential risks associated with forceps deliveries must be balanced against the potential benefits. These risks may affect the mother or the baby.
The possibility of injury to the mother, in the form of vaginal tears or perineum incisions extending to the rectum, increases with rotations of greater than 45 degrees and at higher stations of the fetus's head. However, the likelihood of injury to the perineum is no greater for outlet forceps deliveries than for vaginal deliveries.
Rectal sphincter dysfunction occurs more frequently during forceps deliveries than spontaneous vaginal deliveries. This is due to muscle damage rather than nerve injury; the doctor can minimize this damage by pulling slowly and steadily with the forceps during contractions.
The mother's bladder should always be emptied (usually by catheterization) immediately prior to a planned forceps delivery. This will minimize the risk of inadvertent bladder injury.
Forceps deliveries are also associated with a greater risk for blood transfusion than are spontaneous vaginal deliveries. Although elective (planned) cesarean births are associated with decreased chances of transfusion in comparison to forceps deliveries, emergency cesarean sections are associated with increased chances for transfusion in comparison to forceps deliveries.
Forceps deliveries are associated with an increased risk of injury to the newborn, particularly facial marks or injuries. On the other hand, forceps deliveries are associated with less bruising to the head (cephalohematoma) and retinal bleeding than are vacuum deliveries.
A prolonged second stage of labor should suggest an increased risk of shoulder dystocia. This is a complication of delivery where the baby's head is delivered, but the baby's shoulders are unable to be delivered, usually because the shoulders remain above the pubic bone. Although the frequency of shoulder dystocia is increased in forceps deliveries as compared to spontaneous deliveries, it does occur in spontaneous deliveries and its association with forceps deliveries has not been proven.
Obviously, there is a strong emphasis in this country on pregnancies ending with a healthy mother and baby. There is also clear evidence that the average age of women at their first childbirth is increasing and that the average number of births per woman is decreasing. All of these issues have contributed to the increased frequency of operative deliveries (primarily cesarean births) during the last quarter of the twentieth century.
There are now increasing numbers of health care providers, health care consumers, and health insurance companies who question the high cesarean birth rate and are searching for alternative and safe methods to reduce this rate. In selected cases, it is clear that forceps delivery can, and should, be used instead of cesarean section. When the criteria for forceps delivery are met and when there are appropriate, fetal and/or maternal indications for delivery, such assisted vaginal deliveries are appropriate and safe.